This invention relates to optical analyzing instruments and, more particularly, to optical analyzing instruments for testing samples from the reflective or transmissive properties of the samples.
In U.S. Pat. Nos. 3,861,788, issued Jan. 26, 1977 to Donald R. Webster; and 4,082,464 issued Apr. 4, 1978 to Robert L. Johnson, Jr., there are disclosed instruments for analyzing agricultural samples to determine the percentage of the constituents of the samples, for example, the protein, water and oil content of grain. In the instruments disclosed in these patents, the sample is irradiated with a narrow band wavelength beam of infrared light and the irradiating wavelength is scanned through a range of wavelengths. This is accomplished by an array of interference filters which are successively rotated through a wideband beam of infrared light and are tilted as they each move through the beam of light. This tilting of the interference filters causes the wavelength transmitted by the interference filter to be scanned through a range of wavelengths. At specific selected wavelengths, the intensity of the light reflected from or transmitted by the sample is detected and these intensities are used to determine the constituents in the sample. In the instruments disclosed in the patents, pulses are generated as the array of filters are rotated through the beam of light and are counted by a counter, which provides an indication of the angular position of the array of interference filters. Thus, the counts in the counter will correspond to specific wavelengths transmitted by the filters and irradiating to the sample. These counts are used to automatically select the wavelengths at which the reflected or transmitted intensities are detected and used in the sample analysis.